If you need some evidence that life sciences as a business have emerged in Baltimore, just try to book a downtown hotel room this week.

With 10,000 pediatricians, medical researchers and investors in the health-care industry all in town this week, every room is filled.

Visitors are commuting to downtown from hotels as far away as Hunt Valley and Columbia, staying in bed and breakfasts away from the city's center and searching for apartments that can be used as temporary lodging. One Alex. Brown & Sons executive took a few clients attending the company's health-care conference into his own home.

City officials and business leaders have been promoting the life sciences as the future economic base of the city. But the heart of the city's convention business is already in the medical and high-technology fields. These days, conferences are based on such cutting-edge subjects as genetic engineering and laser and electro-optics.

"It is our single largest major market since the Convention Center opened and it is our largest area of growth," said Wayne Chappell, executive director of the Convention and Visitors Association.

Attracted by the proximity of the Johns Hopkins University and the National Institutes of Health in Bethesda, 4,000 researchers from the American Society of Clinical Investigation came to the city last weekend to present papers on the latest research and listen to speakers such as NIH chief Dr. Bernadine Healy.

Yesterday, as most of the clinical researchers left town, 4,000 pediatricians and pediatric researchers showed up to take their places. The conferences, which were booked eight years ago, were held back-to-back so that visitors could stay for both.

But it was pure coincidence that Alex. Brown & Sons was also holding its 17th annual health-care seminar this week at the Stouffer Harborplace Hotel. More than 100 publicly and privately owned life-science and health-care companies -- from hospital suppliers to biotechnology companies -- are presenting their latest research and innovations to investors and analysts.

About 1,400 people attended the conference, 500 more than showed up two years ago.

The common threads at the conferences were evident yesterday. Just blocks from where Genentech Inc., a California biotechnology company, announced promising test results for a new drug to treat cystic fibrosis this week, the clinical researchers presented papers on the same results.

The conventions have had an immediate and welcome effect on business. "Our cab drivers are starting to smile, our trolleys are filling up, and our limos are getting calls," said Mark Joseph, who heads Yellow Transportation Services.

Harborplace merchants also see the change. "We have noticed the medical convention tags," said Kate Delano, in charge of public relations. "They are buying and eating. It is a significant part of the business."

The city could attract many other conventions if the convention center were expanded to handle twice as many people. About 50 other societies, many of them medical, are eager to come, but there isn't the space, said Mr. Chappell. "Until we expand the convention center, we are about as full as we can be."